Telephone horn



Aug. 4, 1925.

- w. A. DARRAH TELEPHONE HORN Filed May 12 1324 Patented Aug. 4, I925;

WILLIAM A. n mnAH, or cnlceoo, ILLINOIS mnrnonr. BYOB-N.

Application fled m 12,1924. serial No. 712,808.

' To all whom it may concern:

Be it known that I, 'WmmnrA. Darrin, a'citizen of the United States,residim at Chicago, in the county of Cookandsla-te ofIllinois,'haveinvented a new and useful Improvement in Telephone Horns,of

which the following is the specification.

This invention relates-to; coustic devices such as telephone oloud speaers,-an'n on'nc-' ing equipment, phonographs and other sound producing.or.reproducing equipment.

The object. qfthis inventiongxs'to provide astrong,--durable,rjequipment, which er;

which'willi give-:approximately the same ergy input .over}substantially-the entire 4 close the sound producin instrument.

' nits; the emission of =so und waves cinnammum' londness withoutdistortion. Another object of this invention toprovide a horn amplitudeof sound wave for-"the same-enrange of audible' frecfiiencies;

Other objects of't isiinventiouwill a i pear from the 'appendedjdrawinggs and t m specification.

These objects-Lattainby means of the construction and the -.mater1alemployed, as

herein described illustrated.

In the drawings-Figure elevation or my invention looking into. thehorn.' Figure through one form of my invention, the'section being takenon the 1i ne IBB o-Fi ure III. Figure III shows a 'plan view lookin downon my device from the top, igure IV shows a vertical section III. FigureV shows. a detail of the sound passage at a point near the source.'

Referring the drawing (l) indi cates the device, which may be ma e ofporcelain, stoneware, earthenware, .andother hard, dense ceramicmaterials. The materlal must be strong, hard, rigid and preferably havea surface which is smooth and glazed.

The device consists of ahorn which to above and provided with an (3)which' tapers to a constriction (iyand which then continues toreduce ins'ection until at the point (5) it is connected to a source of soundwaves (6), which may be a telephone receiver, a phonograph receiver,

musical device or other soundproduing or reproducing equipment. Forpurposes receiver, and the-device in this case will be referred ,willrespond, more markedly to the I shows a front- II shows. a verticalsection telephone diaphragm.

The housing 11 is created by'a curved formable material, is placedbetween the endofthe horn (5) and the mouthpiece of the telephonereceiver (6). The base of thetelephone receiver (8) is held in.closcunit which is commonly employed contact with the constriction of thehorn (5) bymeans of a resilient member (9) yvbich is fastened by-screw(10) to the housmg (11) ofthehorn; A nut (12) on the screw (10) servesto firinl attach the re- Y silient member (9) to housing (11).

' (-13) represents the wires or leads to the tele hone receiver. (14)indicates the side wa s of the horn, which also serve tonin- These.walls aid in making -t e horn rigid and free from vibrations. (15)represents the tubular constriction connecting threat (4) with orifice(5). (16) represents the rib at the rear of the horn, which at its ends,mer that exten under and are formed integral- ,ly with thebody of thehorn. These ribs lland 11f not only combine to support the horn in itsoperative position butadd its inherent and natural rigidity.

I have foundthat the constriction of AA the horn should pr eierably besuch that the section area a't'any one place changes by an approximatelyconstant exponential factor. This may A, :A ::'K, Where a is a constantexponential function; This arrangement appears togive the minimum lossesby reflection and.

into the longitudinal ribs 11 be illustrated by the formula thereforethe maximum efliciency. arrangement also causes the device to widelydepart from a condition .of resonance or tuning. Resonanceis of courseobjection" able in that the device if tuned 'or resonantfrequencies ofresonanbe than to the other audible frequencies.- For example, astraight tube would be very objectionable owing to its resonatingtendency with asma-ll group tones an of wave lengths. V

I have found that very appreciable losses in horns as well as thepresence as o erd harmonic-s, result from the r (5; materials which canvibrate or yield to the sound energy.

' to that of a-railroadftruui "varying pressure of the sound waves. For(Em-triple, thin sheet metal, by reason of the vibration set up withinthe horn material, rvsu'lts in distorting the'smznd produced andabsorbing an a precia'hle portion of the n the other hand, ughorn' whosewalls are mode of'rig'itl, solid,- glaged porcelain, glass or'heramicmaterials, is not subject to vibrationor motion; under the sorbs none ofthe energjof these waves and does not" introduce res nt,rofiectious or-.distortion or over-tonesf a. i So im ortant i's' this,'factonthatcertain ,inferior orns which are now being made gfroxnpapiermiich and other rclati 'y soft tnetenals, are given a treatmehthi h"herd "Furnish or "shelled, or related: substances, to hat-glen t tovialls' and thereby, someyvhat it'll-j imperfect, As a granhiceillustration of thisprinci ple, -the analogy would be sojmeivliatsimilar p n rubber rails insteadjof steel rails; nthis case, owing tothe com ression of the rubber by the weight of the w the trainwouldcontinually climbing up the hollows in the rails, which-would require a.comparatively extremely large amount of energy;

In the same ,wa to carry the illustration I I to the extreme, 11 cm madeof flexible rub} her would absorb a large aniountof'energy by thecompression endexpansion of the rubber. Many present da ,hornsare sub--jcct to this same difiic ty,.althougl1 of course "in lesser degreesthan'wouldbe a rubber horn. Y I have'found that the ratio between thearea at the orifice (5) and the areaat the mouth of the-horn (3.)shouldbe as great as possible, as this ratio represents 111 a measurethe load effect hpon the diaphragnr of the sound producing instrument.1' have also found that the connection between the sound producinginstrument (6) the critics (5) must be tight and uni- 0TH.-

The device which forms the subject of my invention may preferably beformed in one piece of porcelain, earthernwalre 01' other ceramicmaterial, and will-thus be strong, rigid, durable, and attractive inanpearance. It is preferable that the ceramic unite! ial be glazed,particularly inside of the horn and orifice, although many surprisingresults can be secured without glaze. In the device. which I haveinvented, the horn provides walls or sides which enclose the telephonereceiver or other sound producin device and at the -same time offermeans 0 supporting the horn in place on a table or against the wall.

The horn which I have invented is also relatively stable, not subject toovertones,

involving an u'g y in pearance. infiuence of sound'xvaves, and thereforeabprove themfajlthough' these are stilleti ple, and highly satisfdc b'fii invention. 'For nstance;

.idescribedis considered by me to nuance andis of such form and contourthat it may horn w iich have inyented is tolcastit" in. {i sin 1epieceibiffl q so'e'called castin procnot" wish to be restricted to thismanufacturing method 1tgives"a.-dense,-hrd, smoo A face on the interior.(aha 'eiterioryof the horn The device which I here invented may bemodified in numerous obviou's 'wieysnnd uniform su'rhumero us othermaterials may be listit'uted 0i s "the' .exect without departing fromthe-fifiifi A v W. iormnnd'icontour vvhich'I hovels own-enddesirableform for the commerciolguseof ;this invention, yetthisjinventioii is'broader than the mere shape oifcontourghndcoversmaterials as well; fihusnhorn similar in contour to those nowcommercially employed Lth most.

for radio pur oses but constructed of ceramic materiu as describedfub'ove, I can szde'r to be within the scope of my' nvention'.

Obvious modifications in form and contour will be apparent to thoseskilled-in the art, and these modifications still come'within the scopeof my invention- It should be understood that the 'construc ticn of myhorn asingle, unit isof con-' siderable advantage. in attainingthe'objec-ts of this invention In lot-her, Word's, the smoothcontinuoussurface inside the'horn, free from breaks, crevices or all forms ofdiscontinuities contributc'sto the success of my invention, Further, thefact that the material is the-same for the entire travel of the soundwaves in the horn, is of importance, as I have found that horns mode uof several sections, some of which are meta and somewood onpagier mfich,are less satisfactorv than a. unit construction such es I have invented.It also insures permanence, there are no individual sections to restrictmy invention-to this theory to loosen or lose their shape or alignment.It also appears that the sound wave suffers a lesser distortion onpassing from a section having onc set of characteristics .to a

section of ditl'erent characteristics, as from' metal to'woo'd 0r papiermfich, and vice versa.

.As a theory, which seems plausiblefrom my study of horns, it ispossible that in addition to the rigidity, stifl'ness'and lightness ofceramic materials, the relatively low heat conductivity is one factorwhich serves to make these materials so well suited for sound amplifyingpurposes.- I do not wish am advancing it only as a means f explain;in;'; the superior results secured-by me with horns constructed withceramic materials. I It. will be noted from the drawing that the upper.and lower lips of the horn device project forward beyond the side wallsof the horn. The practical efi'ect of con? noted that'the' largerportion of the horn,

struction is to give a sound-distribution outside the horn which willhave-a greater v'dl ume at points in the'same horizontal plane of thehorn than at points materially above or below the principal axis of thehorn. One 'ell knowndefect of present reproducing devices arises fromthe fact that it the listener is a relatively short distance at one sideof the axis of the sound horn. sounds are much reduce somewhatdistorted. Inasmuch as it is un common for the horn to be placedmaterially below or ahovethe listeners car, the device which I have.invented will distribute the sound throughout the space where it is mostdesired.

In other words, speaking non-technically,

bat -"tumor during the firing the design of my horn is such thatthesound is directedthrou' h a wide angle in a horizontal plane buttrough a relatively arrow angle in a vertical plane. v Another meanswhich I have .fou contributes to the successful operatio of the j horn,is the upwardly turned point or peak in the ,top lip. This peak rves ton'otioe ably reinforce the volume f, thesound in -front of the horn, andfro a manufacturing standpoint materially h lps in thestitfenlng of, theupper wall, which'without'this ,pealc or arcl -construction would have.a tendency tosag'in the' pr of manufacoi the ceramic material; y

j It will also .belnoted; that while the axis of the largerjportionofthe horn is substan- .tially horizon ward the axis?is'substantia1Iylr-vertic2l. It will also'a-bc which is theportionhaving the horizontal axis, is much-o greater in length than'thesmaller-portionlof the horn, or the portion which has the. verticalaxis. I have found the' large portion of the horn, 5' the loadingeffectof the telephondk'liaphragm, the- ,less the distortion and lthe gre terthe volume of sound produced-'- involume and; Ha ing now fully describedmy invention,

or inclined slightly down- Q .the smaller end of the horn that thegreater the length of the axis of the greater what I claim as new andwish to secure by Letters Patent in the follows:

1. A sound amplifier of glazed porcelain. 2. A sound amplifier ofporcelain.

WILLIAM a DARRAH.

United States,- is as

